Baydur 684 is a rigid polyurethane structural foam system used in the reaction injection molding (RIM) process. The system is supplied as two reactive liquid components. Component A is a polymeric diphenylmethane diisocyanate (PMDI), and Component B is a formulated polyol system containing no CFC- or HCFC-blowing additives.

The Baydur 684 system is used for applications requiring high compression strength foams,filling cavities and/or producing foam cores for overmolding. As with any product, use of the Baydur 684 system in a given application must be tested (including field testing, etc.) in advance by the user to determine suitability.